A typical vehicle transmission employs a viscous fluid to lubricate the transmission moving parts, as well as, in some transmissions, to provide hydraulic pressure required to operate the transmission.
Such fluid is generally supplied to the transmission via a dedicated fluid pump driven by a vehicle's engine. The fluid is typically distributed throughout the transmission via a network of fluid passages while the engine is running. However, after the engine has been shut down and has remained off for an extended period of time, the fluid generally tends to drain down from the passages into a transmission sump under the force of gravity. Hence, upon engine restart, the transmission fluid may take an appreciable amount of time to establish sufficient pressure before full transmission operation may resume.